Testing devices which measure tensile stresses on various materials by stretching and/or compressing these materials are used in numerous industries. Essentially, these devices include various means for mounting of the material to be tested such that the material is attached to the testing device at different portions of the material. The material is then stretched or compressed by the device and, for example, the load during stretching or compression is recorded. Known stress/strain testing instruments of this type are marketed by Instron Corporation.
Stress/strain testing devices are used extensively by fiber manufacturers and fiber end users. By carefully stretching, relaxing or otherwise manipulating fibers under controlled conditions, substantial information relating to fiber strength and expected performance can be determined. For example, measurements can be made on fiber strength such as fiber tenacity which is the force required to break a yarn or filament expressed in grams per denier; fiber elongation including the load exerted by the fiber at a certain specified elongation; fiber shrinkage at various temperatures and the like.
Particularly with industrial fibers which are to be used in various highly demanding environments, such as high temperature environments, it is desirable to measure the response of the fibers to various stress/strain conditions under various thermal conditions. Accordingly, various known testing devices such as devices sold by Instron Corporation can optionally include heating and/or cooled environmental testing chambers for conducting tests on the materials, including fibers.
A testing apparatus for the thermal testing of tire cord is disclosed in U.S. Pat. No. 4,998,825 to Hublikar, et al. This device includes a heating cavity which is constructed to receive a sample of tire cord and wherein heating elements surrounding the cavity are controlled by a computerized temperature recorder. A plurality of weights are used to stress the tire cord under various temperature conditions.
U.S. Pat. No. 4,841,779 to Mitsuhashi, et al. discloses a tension tester which includes a central processing unit for controlling a motor which applies test loads to a specimen. The specimen can be retained within a thermostatic chamber including a cooling coil. Video cameras are used to measure the amount of elongation experienced by a specimen and a load cell measures a tensile load applied to the specimen.
U.S. Pat. No. 4,335,615 to Kalfa, et al. discloses a device for testing materials for stress corrosion cracking in which a pair of rotary stepping motors are used to impart a tensile load to a test sample. The rotary stepping motors are connected via a planetary gear system to the test sample for the application of controlled stress to the sample.
U.S. Pat. No. 3,813,919 to Taniguchi, et al. discloses a testing apparatus for measuring thermal behaviors of filament yarn. This apparatus includes a tube heater which encloses a test specimen. A spiral resistor and air cooling blower are employed for maintaining the specimen at a predetermined temperature. The temperature of the specimen is said to be capable of being increased or decreased rapidly by an electronic temperature controller.
Although these and other known testing apparatus provide the capability for performing various controlled tests on fibers, the known devices can include various drawbacks including the requirement for multiple testing devices in order to perform various different tests. Many of the devices are large and complex. For example, those systems which are highly accurate can typically include gearing systems, mounting systems and the like such that the apparatus can be extremely large. Similarly, with those systems that the test parameters can be varied as chosen by the user of the system, the various parts and portions of the system result in a complete system which is highly complex. Systems are not readily available which are highly accurate, of relatively small size and are capable of varying mechanical testing parameters and temperature conditions during a single test at the option of the user or according to one or more sets of predetermined instructions.